Level luffing attachment for cranes



May 26, 1959 R. P. FOX

LEVEL LUFFING ATTACHMENT FOR CRANES Filed Nov. 16, 1954 INVENTOR Qfioker'f I? fbx 1 BY m ATTORNEY LEVEL LUFFING ATTACHlVlENlF FOR 'CRANESRobert P. Fox, Duluth, Minn., assignor to 'Clyde Iron Works, Inc.,Duluth, Minn, a corporation of Minnesota Application November 16, 1954,Serial No. 469,161

3 Claims. (Cl. 212-58) This invention relates to an improvement in levellufiing attachment for cranes, and deals particularly with an attachmentwhich can be added to a standard crane of the Whirley type withoutimpairing the normal capability of the main or heavy tackle.

For many years, the advantage of level luffing gear on cranes designedfor certain uses has been recognized. Numerous types of gear has beenproduced to accomplish this result. In general, in a level luflingcrane, the load traverses a horizontal path as the boom of the crane isluifed from maximum to minimum radius. High speed operation without lossof safety and control is possible, and the swinging and lufling of theboom may be easily coordinated by an operator having limited experience.Perhaps the greatest advantage of this type of gear, however, lies inthe fact that little lutfing power is required, since the load is notlifted as the boom is raised.

While level luffing cranes have been in use for some years, such cranesare designed specially for this purpose, and cannot be used as allpurpose cranes. It is the purpose of the present invention to provide anattachment to a crane of conventional type which is capable oftransforming a conventional crane into a level lufiing crane, whilestill not interfering with the normal operation of the crane when it isbeing used for heavier loads.

A feature of the present invention lies in the provision of a simple andinexpensive attachment for a standard crane which may be used inconjunction with an extra line to provide a level luffing action on theconventional crane. As a result, a single crane may serve both purposes,and much of the heavy expense involved in having available cranes ofboth types may be eliminated.

A further feature of the present invention lies in the provision of asimple attachment for cranes which may provide a level lufiing gear forstandard cranes, and which may accommodate either a single line with ahook attachment, or a two line clam shell bucket. The attachment is alsoreadily changed in design to accommodate various boom lengths by raisingor lowering the tackle suspension point.

These and other objects, and novel features of the present inventionwill be more clearly and fully set forth in the following specificationand claims:

In the drawings forming a part of the specification;

The figure is a side elevational view of a crane, showing the levellufiing attachment in place thereupon.

In view of the large actual size of the crane, the draw ing is not shownin great detail. However, the attach ment is believed shown insuificient detail so that the invention will be clear to those skilledin the art. The particular crane illustrated is of the type knowncommercially as a Whirley, being mounted at the top of a moveable gantryonly diagrammatically shown in partial form in the drawings. The gantrysupports a circular track 10, and the base of the crane is circular, andis supported by suitable wheels or wheel trucks 11 so that the crane mayrotate about a vertical axis.

States Patent The wheels or wheel trucks 11 support a crane base 12which is rotatably supported upon the circular track 10 for swingingmovement about a vertical axis. A pair of upwardly inclined rear mastportions 13, one of which is shown in the figure, extend upwardly frompoints 14 on the crane base to provide a mast. A second pair of mastforming members 15, one of which is illustrated in the figure, extendupwardly from point 16 near the forward end of the crane base. The upperends of the members 13 and 15 are connected together at the mast top 17.v,

The crane boom 19 is pivotally connected at 20 along a transverse axisat the forward end of the crane platform 12 to extend forwardlytherefrom. The lufiing attachment for the crane includes a sheaveblock21 which is pivotally connected to the mast at the mast top 17 Theluffing gear also includes a second sheaveblock 22 which is connected bya fixed length of line 23 to a bridle strap 24 which is hingedlyconnected at 25 to the boom 19 near the point thereof. The luffing lineextends from the luffing drum 26 over a direction changing the sheave 27on the forward frame portions 15 of the mast, over the outer sheave 29of the sheave block 22, around the larger sheave 30 of the sheave block21, back around the sheave 31 of the sheave block 22, next around thesheave 32 of the sheave block 21, and is deadended to the sheave block22 at 33. Accordingly, when a pull is exerted upon the luffing block 34,the sheave block 22 is drawn toward the sheave block 21, thus, swingingthe boom up wardly to position the boom point at a smaller radius fromthe center of rotation of the crane frame.

The main or heavy tackle of the crane is also conventional. The loadline 35 extends from the hoisting drum 36 between a pair of guidesheaves 37 and along the boom to the sheave 39 at the boom point orspaced slightly therefrom. The line 35 then extends down through theload block, and upwardly through the load block 41, the line passingover any desired number of sheaves in the two blocks and being deadendedto one of the blocks as is indicated at 42. A hook 43 is shown connected to the block 40 for supporting a load and the upper block 41 isconnected below the boom point by asuitable hanger 44. This main tackleis standard upon cranes of this type and is, of course, capable oflifting extremely heavy loads.

The level luffing attachment for the crane will now be" described. Theboom is extended either by a separate ex'- tension 45 or by spacing thesheave 39 at a point spaced from the extreme point of the boom. Framemembers 46 extend upwardly from the forward part of the crane body andcooperable frame members 47 are hinged to the mast part 15 at 49 and areconnected to the frame parts 46 at 50. A sheave S1 is mounted at thispoint and a direction changing sheave 52 is provided near the lower endsof the frame parts 46 to guide the load line 53 from the sheave 51 tothe load drum 54.

The boom extension 45 supports a first sheave 55 and a second sheave 56.The level luihng line 53 extends from the drum 54 between the guidepulleys 52 and over the sheave 51. From here the line extends over thesheave and back around a second sheave 51 parallel to the first sheave.The line then extends over the sheave 56 and downwardly to the bucket 57or other load supporting device.

Thus it will be seen that the single part load line is reeved into threeparts between the sheave 51 and the sheave 55. The sheave 51 is locatedat the one point from which the distance to the boom point sheave 55reduces by exactly one-third the amount that the boom point is elevatedas the boom is raised. The location of the sheave 51 is determined by agraphic construction aeeawo employing the fact that the resultant of avertical force of one combined with a topping force of three must passthrough the boom point. As a result of this atrangement, as the boom 19is elevated, the three part line between the sheaves 51 and 55 hold theload 57 at a constant elevation from the position shown in full lines tothe position shown in dotted lines which represent the point of minimumradius of the load.

Thus as will be indicated from the drawings, if the load comprises aclam shell bucket the load may be lifted to the level shown in fulllines and moved horizontally to the position shown in dotted lines so asto drop the load into the hopper 60 which forms a part of the base orsupport 61 of the crane.

The advantage of this arrangement is believed obvious. Under normalcircumstances one type of crane must be used for the lifting of heavymaterials so that in such a case it is necessary to use the main tackleof the crane where high loads such as in the nature of ten to onehundred tons are to be lifted depending upon the crane model. However,when loads under ten tons are lifted and where level luifing isdesirable for the quick handling of cargo, the level luffing attachmentmay be employed. Neither tackle affects the use or operation of theother and a single crane is capable either of unloading by level lufiingmethods or by ordinary crane operation.

It will be seen that the level luffing attachment is readily adaptableto cranes of the Whirley type and the attachment is merely constructedto properly locate the point at which the sheave 51 is supportedrelative to the sheave 55. In speaking of the sheave 51 it will beunderstood that more than one sheave is mounted in side by side relationto accommodate the three part line. In instances where the load line 35passes about a tackle block and is dead ended at the boom point to forma two part line, the three part reeving is doubled. In constructing theattachment the boom point extension 45 is planned for the end of theboom and the point 50 is located graphically so that the level luffingline 53 pays out the amount which the boom raises.

While the location of the point 50 varies for each crane having adifferent mast height and boom length, little difficulty is experiencein determining the point of location as cranes of the type in questionare usually furnished in a series of standard boom lengths andcorresponding mast heights.

In accordance with the patent statutes, I have described the principlesof construction and operation of my level lutfing attachment, and whileI have endeavored to set forth the best embodiment thereof, I desire tohave it understood that obvious changes may be made within the scope ofthe following claims without departing from the spirit of my invention.

I claim:

1. A level luffing attachment for conventional cranes of the type havinga base, a mast extending upwardly from the base, a boom pivotallysupported upon the base for movement in a vertical plane, means forraising and lowering said boom, a main sheave means carried by saidboom, and a main load line extending over said main sheave means, theattachment including a pair of frame members one of which is connectedto the crane base to extend upwardly therefrom, and the other of saidframe members being connected to the crane mast and extending forwardlytherefrom to intersect said first frame member, the frame members beingconnected together, an extension connected to the upper end of saidboom, a first auxiliary sheave means supported at the free end of saidextension to form a boom point, a second auxiliary sheave meansconnected to the intersection of said frame members, a three partauxiliary load line extending between said first and second sheavemeans, a hoisting drum to which one end of said auxiliary load line issecured, the other end of said auxiliary load line extending downwardlyfrom said first named auxiliary sheave means, said second sheave meansbeing located at the one point from which the distance to the boom pointreduces by one-third the amount that the boom is elevated as the boom israised.

2. A level lufiing attachment for conventional cranes having a cranebase, a mast extending upwardly from the crane base, a boom pivotallysupported by the base for movement in a vertical plane, means forraising and lowering said boom, a main sheave means carried by saidboom, and a main load line extending over said main sheave means, theattachment including a first auxiliary sheave means at the boom point, aframe connected to the mast supporting a secondary auxiliary sheavemeans, a three part auxiliary load line extending over said first andsecond auxiliary sheave means, a hoist drum connected to one end of saidauxiliary load line, the other end of the auxiliary load line extendingdownwardly from the boom point, the second auxiliary sheave means beinglocated at the point where the distance between the sheave and the boompoint reduces .by exactly one-third the amount the boom point iselevated when the boom is raised, said frame supporting said secondsheave means being also detachably connected to the crane base.

3. A level lufiing attachment for cranes of the type having a base, amast extending upwardly from the base, a boom pivotally supported uponthe base for movement in a vertical plane, means for raising andlowering said boom, the attachment including a pair of frame members oneof which is connected to the crane base to extend upwardly therefrom,and the other of the frame members being connected to the crane mast andextending forwardly therefrom to intersect the first frame member, theframe members being connected together, an extension on the upper end ofsaid boom, a first sheave means supported at the free end of saidextension to form a boom point, a second sheave means connected to theintersection of said frame members, a three part load line extendingbetween said first and second sheave means, a hoisting drum connected toone end of said load line, the other end of the load line extendingdownwardly from said first named sheave means, said second sheave meansbeing located at the one point from which the distance to the boom pointreduces by one-third the amount that the boom is elevated as the boom israised.

References Cited in the file of this patent UNITED STATES PATENTS2,082,017 McClain June 1, 1937 2,386,475 Kay Oct. 9, 1945 2,570,417Wulleman Oct. 9, 1951 2,703,180 Brown Mar. 1, 1955 FOREIGN PATENTS196,056 Great Britain Apr. 11, 1923 760,662 France Dec. 14, 1933

